1. Field of the Invention
The present invention relates to, in general, a fire grate assembly for stoker incinerators, and more particularly, to a fire grate assembly capable of preventing stationary and movable grate members from coming into direct contact with each other resulting in deteriorating wear, thus allowing the grate members to be free from being changed with new ones.
2. Description of the Prior Art
As well known to those skilled in the art, conventional incinerators for burning refuse are typically classified into three types: stoker incinerators, rotary kiln incinerators and fluidized bed incinerators. The three types of incinerators are selectively used according to the kind of refuse and desired refuse treatment capacity.
Generally, stoker incinerators are preferably used for burning large amounts of municipal refuse, while fluidized bed incinerators are in the early stages of being used practically.
Such stoker incinerators are classified into various types according to both the types of fire grate assemblies and the construction of combustion furnaces. When such fire grate assemblies are designed, it is necessary to consider the installation area of a stoker incinerator, calorific power of refuse, the circulation type of combustion gas, and configuration and expected loaded conditions of the grate assembly, such as the weight of the load, because the operational functions and characteristics of such fire grate assemblies are different from each other.
FIG. 1 is a schematic view showing the construction of a conventional stoker incinerator.
As shown in FIG. 1, refuse, piled up in a refuse pit 2, is primarily measured prior to being fed into a hopper 4 by a traveling crane 3. Thereafter, the refuse of the hopper 4 are moved to the top portion of a fire grate assembly 6. The refuse is mixed with the previously burnt refuse of the grate assembly 6, thereby being dried and burnt simultaneously. In addition, the refuse, disposed at the top portion of the grate assembly 6, is gradually moved to the bottom portion of the fire grate assembly 6. Ashes, produced from the refuse completely burnt during the movement of the refuse along the grate assembly 6, are dropped into a re-treatment facility by a clinker roller 33 of FIG. 2 and are fed into an ash bunker 8.
Primary combustion air or atmospheric air, necessary for the incineration of the refuse, is forcibly intaken into the grate assembly 6 through the refuse pit 2 by a force draft fan 7, thereby preventing noxious odor from being exhausted into the atmosphere. In such a case, the intaken primary combustion air is heated by an air heater prior to being introduced into a combustion chamber of the incinerator through the fire grate assembly. The intaken air is divided into four to six sections capable of being separately controlled.
In addition, secondary combustion air, which is about 20 to 40% of the supplied air, is discharged from the side portion of the incinerator into the combustion chamber, thereby completely incinerating the incompletely burnt refuse. Combustion gas, having a high temperature and being produced from the burnt refuse, passes into a combustion. gas cooling facility and an exhaust gas treatment facility through first and second combustion chambers.
The incinerator also comprises a boiler facility 11 and an antipollution facility, including both a dust collector 13 and a stack 15. The boiler facility 11 is used for recovering heat from the combustion gas and cooling the gas, while the antipollution facility is used for removing pollutants from the combustion gas. Also, the incinerator further comprises subsidiary facilities, such as conveyer equipment for feeding, piling up and discharging dusts and ashes, a sewage treatment facility for biologically or chemically treating sewage from the incinerator, plumbing equipment for supplying water into the incinerator and draining sanitary sewage, and supply equipment for feeding compressed air and fuels, etc.
Thus, it is necessary to maintain the temperature of the combustion gas, introduced from a cooling device, lower than 300C so as to prevent the above equipment and facilities from being corroded.
FIG. 2 is a view illustrating the fire grate assembly 6 for feeding and agitating the refuse.
The grate assembly 6 comprises a plurality of uniformly-spaced stationary and movable grate members 31 and 32, which are alternately and inclinedly arranged in the assembly 6.
The movable grate members 32 push upwardly the lower portion of the refuse. However, the refuse, disposed at the top portion of the grate assembly 6, is also moved downwardly along the assembly 6 due to gravity. Therefore, the refuse is moved upwardly and downwardly, thus being effectively agitated.
The stationary grate members 31 are fixedly mounted to the incinerator, while the movable grate members 32 are movably mounted to the incinerator in such a manner that they reciprocate linearly while being in contact with the stationary grate members 31, respectively. Due to such a linear reciprocating motion of the movable grate members 32, the refuse on the fire grate assembly 6 is continuously agitated, thereby effectively improving the refuse combustion efficiency.
However, the stationary and movable grate members 31 and 32 are brought into frictional contact with each other and the movable members 32 are moved on the top surfaces of the stationary members 31. Thus, each surface of the stationary and movable grate members 31 and 31 is irregularly abraded.
Therefore, the above fire grate assembly is problematic in that the combustion pressure of the incinerator is reduced because the primary burning air, supplied to the grate assembly 6 upwardly, leaks through the gaps defined between the abraded surfaces of the grate members 31 and 32. Also, the movable grate members 32 may fail to effectively perform their linear reciprocating motion and fail to mix the refuse because the refuse is introduced into the gaps between the abraded surfaces of the grate members 31 and 32. In such a case, the refuse is incompletely burnt. As a result, poisonous gas may be generated, which is harmful to the human body.
Such abraded grate members 31 and 32 require frequent changing with new ones, thus shortening the life span of the fire grate assembly and forcing the owner to replace an existing grate assembly with a new one at excessive costs.